Correspondence
Correction
Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet
N Engl J Med 2008; 359:2169-2172November 13, 2008
- Article
To the Editor:
How do Shai et al. (July 17 issue)1 explain why the subjects in their study regained weight between month 6 and month 24, despite a reported reduction of 300 to 600 calories per day? Contributing possibilities may include the notion that a food-frequency questionnaire cannot precisely determine energy or macronutrient intake but, rather, ascertains general dietary patterns. Certain populations may underreport intake2,3 and have a decreased metabolic rate. The authors did not measure body composition, which is critical for documenting weight-loss components.
In addition, the titles of the diets that are described in the article are misleading. Labeling the “low-carbohydrate” diet as such is questionable, since 40 to 42% of calories were from carbohydrates from month 6 to month 24, and data regarding ketosis support this view. Participants in the low-fat and Mediterranean-diet groups consumed between 30% and 33% of calories from fat and did not increase fiber consumption, highlighting the importance of diet quality. Furthermore, the authors should have provided baseline values and P values for within-group changes from baseline (see Table 2 of the article).
Contrary to the authors' assertion, it is not surprising that the effects on many biomarkers were minimal, since the dietary changes were minimal. The absence of biologically significant weight loss (2 to 4% after 2 years) highlights the fact that energy restriction and weight loss in themselves may minimally affect metabolic outcomes and that lifestyle changes must incorporate physical activity to optimize the reduction in the risk of chronic disease.4,5
5 ReferencesChristian K. Roberts, Ph.D.
R. James Barnard, Ph.D.
Daniel M. Croymans, B.S.
University of California, Los Angeles, Los Angeles, CA 90095-1606
croberts@ucla.edu 1
Shai I ,Schwarzfuchs D ,Henkin Y , et al. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med 2008;359:229-241
Full Text | Web of Science | Medline2
Schoeller DA . Limitations in the assessment of dietary energy intake by self-report. Metabolism 1995;44:Suppl 2:18-22
CrossRef | Web of Science | Medline3
Neuhouser ML ,Tinker L ,Shaw PA , et al. Use of recovery biomarkers to calibrate nutrient consumption self-reports in the Women's Health Initiative. Am J Epidemiol 2008;167:1247-1259
CrossRef | Web of Science | Medline4
Roberts CK ,Barnard RJ . Effects of exercise and diet on chronic disease. J Appl Physiol 2005;98:3-30
CrossRef | Web of Science | Medline5
Booth FW ,Chakravarthy MV ,Gordon SE ,Spangenburg EE . Waging war on physical inactivity: using modern molecular ammunition against an ancient enemy. J Appl Physiol 2002;93:3-30
Web of Science | Medline
To the Editor:
Shai and colleagues found that a low-fat diet was less effective than either a Mediterranean diet or a low-carbohydrate diet in achieving weight loss. However, the “low-fat” group was actually not instructed to follow a low-fat diet, because the diet composition (i.e., calories from fat) did not change during the intervention. So, in reality, since the members of this group consumed the same diet as they did habitually, it should have been called the control group. Weight loss is known to occur as a consequence of reducing the proportion of calories from fat,1 so the design of the study was not really fair to the low-fat diet. Moreover, the dropout rate was 15% in the Mediterranean group, 22% in the low-carbohydrate group, and only 10% in the low-fat group (P=0.04). In a study involving Danish subjects,2 my colleagues and I also observed that there was a significantly higher dropout rate among participants on a Mediterranean diet (28%) than among those on a (real) low-fat diet (16%), after both 6 months and 18 months. Retention is an end point that deserves comment.
Arne Astrup, M.D.
University of Copenhagen, 1958 Frederiksberg, Denmark
ast@life.ku. dk Dr. Astrup reports receiving consulting fees from Weight Watchers and Global Dairy Platform and reports that his department at the University of Copenhagen has received research funding from many food companies. No other potential conflict of interest relevant to this letter was reported.
2 References1
Astrup A ,Grunwald GK ,Melanson EL ,Saris WHM ,Hill JO . The role of low-fat diets in body weight control: a meta-analysis of ad libitum intervention studies. Int J Obes Relat Metab Disord 2000;24:1545-1552
CrossRef | Web of Science | Medline2
Due A, Larsen TM, Mu H, et al. Comparison of three ad libitum diets for weight loss maintenance, risk for CVD and diabetes: a 6 month randomised, controlled trial. Am J Clin Nutr (in press).
To the Editor:
Shai et al. report that either a Mediterranean diet or a low-carbohydrate diet was an effective alternative to a low-fat diet in terms of weight loss. Absolute values for the energy intake before and after the intervention are not given for any of the groups. However, the data provided in the article suggest that the weight loss in the low-carbohydrate group may have been simply a hypocaloric effect, even though the authors state that the energy intake in this group was not restricted. Thus, if the daily intake of carbohydrates was no more than 120 g (equal to 500 kcal), as stated in the Methods section, and if the fraction of the energy intake provided by carbohydrates was around 40%, as stated in Table 2, then the total daily energy intake in the low-carbohydrate group must have been no more than approximately 1250 kcal, which is significantly less than the daily intake targeted for the two other groups.
Kirsten Moller, M.D., Ph.D.
Rikke Krogh-Madsen, M.D., Ph.D.
University Hospital Rigshospitalet, DK-2100 Copenhagen, Denmark
kirsten.moller@dadlnet. dk To the Editor:
In the study by Shai et al., participants who were on the low-fat diet decreased their total fat intake from 31.4% to 30.0% — in other words, hardly at all. It is important to measure disease end points, not just risk factors. Greater increases in high-density lipoprotein (HDL) cholesterol among patients on the Atkins diet may not necessarily be beneficial, as the torcetrapib study indicated.1 Very-low-fat diets may reverse coronary heart disease2 and prostate cancer3 and also improve gene expression,4 despite reductions in HDL cholesterol, whereas flow-mediated vasodilatation, a measure of endothelial function and a predictor of cardiovascular events, worsened among subjects on the Atkins diet.5
In the “Atkins diet” that was tested by Shai et al., the authors state that they counseled the study participants to choose vegetarian sources of fat and protein and to avoid trans fat. However, such a diet is not representative of the Atkins diet, which recommends bacon, butter, and brie, not fruits and vegetables. Why were the participants counseled to do this?
Dean Ornish, M.D.
University of California, San Francisco, San Francisco, CA 94143Dr. Ornish reports writing general-interest books on health and wellness (including diet) for which he receives royalties. He also reports receiving lecture fees from the Harry Walker speaker's bureau and consulting fees from PepsiCo, Mars, and Safeway. No other potential conflict of interest relevant to this letter was reported.
5 References1
Barter PJ ,Caulfield M ,Eriksson M , et al. Effects of torcetrapib in patients at high risk for coronary events. N Engl J Med 2007;357:2109-2122
Full Text | Web of Science | Medline2
Ornish D ,Scherwitz LW ,Billings JH , et al. Intensive lifestyle changes for reversal of coronary heart disease. JAMA 1998;280:2001-2007[Erratum, JAMA 1999;281:1380.]
CrossRef | Web of Science | Medline3
Ornish D ,Weidner G ,Fair WR , et al. Intensive lifestyle changes may affect the progression of prostate cancer. J Urol 2005;174:1065-1070
CrossRef | Web of Science | Medline4
Ornish D ,Magbanua MJM ,Weidner G , et al. Changes in prostate gene expression in men undergoing an intensive nutrition and lifestyle intervention. Proc Natl Acad Sci U S A 2008;105:8369-8374
CrossRef | Web of Science | Medline5
Miller M ,Beach V ,Mangano C , et al. Comparative effects of 3 popular diets on lipids, endothelial function and biomarkers of atherothrombosis in the absence of weight loss. Circulation 2007;116:II-819
To the Editor:
Shai et al. report very low attrition rates among study participants, and this is surely a good point, given the 2-year length of the study. The authors properly recognize that this finding is probably due to a closely monitored intervention, but they do not report anything about the costs of their face-to-face, dietitian-based approach. As noted by Glasgow and Emmons,1 among factors that impede the translation of research into widespread practice, important obstacles are the high cost and large time demands on both staff and participants. Even if the authors' strategies for maintaining adherence could be applied outside the workplace, we are not as optimistic as they are, considering the low cost-effectiveness that usually characterizes face-to-face approaches targeting eating habits.
1 ReferencesGian Mauro Manzoni, Psy.D.
Gianluca Castelnuovo, Ph.D.
Enrico Molinari, Ph.D.
Istituto Auxologico Italiano, 28824 Piancavallo, Italy
gm.manzoni@auxologico. it 1
Glasgow RE ,Emmons KM . How can we increase translation of research to practice? Types of evidence needed. Annu Rev Public Health 2007;28:413-433
CrossRef | Web of Science | Medline
Author/Editor Response
Roberts and colleagues correctly note that a food-frequency questionnaire cannot precisely assess exact caloric intake. In our study, we used identical nutritional values for each of the 137 questionnaire items, irrespective of the specific dietary intervention. For example, “vegetable soups” were not specially analyzed within the low-fat group as “no fat added” or in the low-carbohydrate group as “creamed” or “no starch added.” Thus, although the questionnaire data revealed three distinct dietary regimens throughout the intervention, these data might have underestimated the true differences among the groups. Correlations between data from food-frequency questionnaires and those from 24-hour dietary recalls, which were used in a subgroup of participants, were more than 0.8 for most nutrients.
In response to the letters from Astrup and Moller and Krogh-Madsen: the diet-recall data confirm that the total caloric deficit was similar among the groups and that the low-fat group maintained a relatively low intake of fat (Table 1Table 1
Dietary Intake from 24-Hour Dietary Recall among Participants in the Dietary Intervention Randomized Controlled Trial (DIRECT).). Obviously, with a substantial total caloric deficit, the absolute consumption of fiber was decreased; however, the decrease in the low-fat group was half of that in the low-carbohydrate group.We agree with Roberts et al. on the importance of physical activity, but our study specifically focused on diet composition. Roberts et al. are incorrect in characterizing the weight loss as biologically not meaningful, since it yielded clinically important changes in risk factors. Intriguingly, the weight reduction achieved among the moderately obese subjects in our study was identical to that reported in a recent meta-analysis on long-term pharmacotherapy for obesity.2
In response to Ornish's letter: the low-carbohydrate diet was based on Atkins's book, although we encouraged the study participants to consume a variety of protein and fat sources to maintain successful long-term adherence. We specifically reported on retention in detail and noted that adherence was higher in this trial than in any other trial of a similar length that we know of. The setting and methods we used to maximize adherence rates permitted a robust test of the three dietary strategies, as assessed by weight loss and established measurements of lipids, glycemic control, and hepatic and inflammatory biomarkers. As noted by Manzoni and colleagues, we did not assess cost-effectiveness. However, we believe that cost-effective interventions can be implemented in the workplace, with the use of group meetings and by working with food-service providers.
Several readers have informed us that our online Supplementary Appendix was incomplete. We have updated the appendix to provide more complete information.
2 ReferencesIris Shai, R.D., Ph.D.
Ben-Gurion University, Beer-Sheva 84105, Israel
irish@bgu.ac. il Yaakov Henkin, M.D.
Soroka University Medical Center, Beer-Sheva 84101, IsraelMeir J. Stampfer, M.D., Dr.P.H.
Harvard Medical School, Boston, MA 021151
Shai I ,Vardi H ,Shahar DR , et al. Adaptation of international nutrition databases and data-entry system tools to a specific population. Public Health Nutr 2003;6:401-406
CrossRef | Web of Science | Medline2
Rucker D ,Padwal R ,Li SK ,Curioni C ,Lau DC . Long term pharmacotherapy for obesity and overweight: updated meta-analysis. BMJ 2007;335:1194-1199
CrossRef | Web of Science | Medline
- Citing Articles (1)
Citing Articles
1
Anjali A Dixit, Kristen MJ Azar, Christopher D Gardner, Latha P Palaniappan. (2011) Incorporation of whole, ancient grains into a modern Asian Indian diet to reduce the burden of chronic disease. Nutrition Reviews 69:8, 479-488
CrossRef
